The present invention relates to a method for making aromatic ether imides. More particularly, the present invention relates to the reaction of a halo-substituted phthalamide and anhydrous alkali metal phenoxide salt in the absence of an organic solvent and at a temperature at least sufficient to convert the halo-substituted phthalimide to the molten state.
Prior to the present invention, methods for making aromatic ether imides were generally based on the use of a dipolar aprotic solvent or non-polar aprotic solvent in conjunction with a phase transfer catalyst. For example, U.S. Pat. Nos. 3,879,428, 3,957,862 and 3,956,320, to Heath et al and U.S. Pat. No. 3,956,125 to Meyers form such compounds by condensation of an alkali metal phenoxide with a nuclear substituted phthalimide in the presence of a dipolar aprotic solvent. Additional methods for making aromatic ether imides are shown by Williams U.S. Pat. No. 4,273,712, Williams et al, U.S. Pat. No. 4,252,953 and Relles et al, U.S. Pat. No. 4,247,464, assigned to the same assignee as the present invention.
It would obviously be a substantial benefit to the art if aromatic ether imides could be formed without the necessity for using solvents which are expensive, require recycling and often require redistillation for reuse, in addition to leading to the possibility of chemical side reactions.
The present invention is based on the discovery that reaction can be effected between a halogen-substituted phthalimide of the formula, ##STR1## and an anhydrous alkali metal phenoxide salt of the formula, EQU R.sup.1 --(OM).sub.a ( 2)
where R is a monovalent radical selected from hydrogen, a (C.sub.1-8) alkyl radical and a C.sub.(6-13) aryl radical, R.sup.1 is a C.sub.(6-30) aromatic organic radical, X is chlorine, bromine or fluorine, preferably chlorine or bromine and most preferably chlorine, and M is an alkali metal ion, in the absence of an organic solvent by heating a mixture of these two components at a temperature in excess of the melting point of the halogen-substituted phthalimide. The use of a phase transfer catalyst has been found optional in the aforementioned reaction.